JP2012121520A - On-board device and key identification method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an on-board device which can be operated simply by various remote controllers.SOLUTION: A voltage detecting part 22 includes an input port IN connected to a partial pressure type remote controller 6 for outputting voltages different from each other for each of key depressed by a user, and detects through the input port IN the voltage output from the partial pressure type remote controller 6. A pull-up resisting part 21a is connected in series between the input port IN and a power supply Vdd for outputting a voltage to the partial pressure type remote controller 6, and has a variable resistance value. A control part 23 controls the pull-up resisting part 21a to have a plurality of resistance values sequentially changed while the key remains depressed. A processing part selects a resistance value of the pull-up resistor on the basis of output voltages given respectively for a plurality resistance values while the key remains depressed.

Description

  The present invention relates to an in-vehicle device that can be operated by various remote controllers and a key identification method.

Vehicles such as automobiles may be equipped with vehicle-mounted devices such as so-called genuine car navigation devices and car audio devices certified by vehicle manufacturers. An increasing number of vehicles are equipped with a remote controller for remotely controlling a genuine in-vehicle device on the steering wheel.
A remote controller (hereinafter referred to as a steering remote controller) mounted on the steering wheel is set so as to control a genuine in-vehicle device.

  There is a case where a genuine in-vehicle device is replaced with another on-vehicle device that is generally marketed. The signal (voltage value) output from the steering remote controller is set corresponding to a genuine in-vehicle device, and the voltage value may differ depending on the vehicle manufacturer and vehicle type. Therefore, even if the steering remote controller is connected to a commercially available on-vehicle device, the commercially available on-vehicle device cannot be appropriately operated.

  Therefore, an adapter has been proposed in which a signal from a steering remote controller is input, converted into a signal that can be handled by the vehicle-mounted device, and supplied to the vehicle-mounted device (see Patent Documents 1 and 2).

JP 2007-320360 A JP 2007-230290 A

It is desired that the vehicle-mounted device can be set to be operable by the steering remote controller in the vehicle-mounted device main body instead of the adapter described in Patent Documents 1 and 2. In addition, it is desirable to be able to cope with a plurality of steering remote controllers from a plurality of vehicle manufacturers and to be set so that the in-vehicle device can be operated.
An object of the present invention is to provide an in-vehicle device that can be set to be operable by an external remote controller in the in-vehicle device body. Moreover, it aims at providing the vehicle-mounted apparatus which can set an own apparatus so that operation is possible corresponding to several remote controllers by several vehicle manufacturers. Furthermore, it aims at providing the key identification method which can identify the key provided in the remote controller with few misidentification.

  In order to achieve the above object, a first aspect of the present invention includes an input port connected to a voltage-dividing remote controller (6) that outputs a different voltage for each key pressed by a user, and from the input port The voltage detector (22) for detecting the voltage output from the remote controller (6) and the power source for outputting the voltage to the remote controller (6) and the input port are connected in series, and the resistance value is variable. A certain pull-up resistor unit (21a), a control unit (23) that controls the pull-up resistor unit (21a) to sequentially change to a plurality of resistance values, and the key are pressed while the key is pressed. The gist of the present invention is an in-vehicle device including a processing unit (3) that selects a resistance value of the pull-up resistor unit (21a) based on an output voltage for each of a plurality of resistance values.

  According to a second aspect of the present invention, a step of detecting a voltage output from a remote controller from an input port connected to a voltage dividing type remote controller that outputs a different voltage for each key pressed by a user, A step of controlling the pull-up resistor unit, which is connected in series between the power source that outputs a voltage to the remote controller and the input port and has a variable resistance value, to sequentially change to a plurality of resistance values while being pressed. And the step of selecting the resistance value of the pull-up resistor unit based on the output voltage from the remote controller for each of a plurality of resistance values while the key is pressed, and the state of selecting the resistance value of the pull-up resistor unit And identifying the pressed key based on the output voltage output from the remote controller. To.

  ADVANTAGE OF THE INVENTION According to this invention, it can set so that an own apparatus can be operated with an external remote controller with a vehicle-mounted apparatus main body. Further, the device can be set to be operable in correspondence with a plurality of remote controllers by a plurality of vehicle manufacturers. Furthermore, it is possible to identify the key provided on the remote controller with little misidentification.

It is a typical block diagram explaining the basic composition of the vehicle equipment concerning a 1st embodiment of the present invention. It is a figure explaining the detection process part and steering remote control of the vehicle-mounted apparatus which concern on the 1st Embodiment of this invention. It is a figure explaining the method for the vehicle-mounted apparatus which concerns on the 1st Embodiment of this invention to detect the output signal of a steering remote control. It is a flowchart explaining the key allocation method which concerns on the 1st Embodiment of this invention. It is an example which illustrated the touchscreen screen in order to demonstrate the key allocation method which concerns on the 1st Embodiment of this invention. It is a typical block diagram explaining the basic composition of the vehicle-mounted apparatus which concerns on the 2nd Embodiment of this invention. It is a circuit diagram explaining the difference in the structure of the steering remote controller by the vehicle manufacturer. It is a figure explaining the difference in the output voltage of the steering remote control by a vehicle maker. It is a circuit diagram explaining the pull-up resistance part of the vehicle-mounted apparatus which concerns on the 2nd Embodiment of this invention. It is a flowchart explaining the determination method of the resistance value of the pull-up resistance part of the vehicle-mounted apparatus which concerns on the 2nd Embodiment of this invention.

  Next, first and second embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, the following embodiments exemplify devices and methods for embodying the technical idea of the present invention, and systems using these devices. The technical idea of the present invention is as follows. The present invention is not limited to the devices and methods exemplified in the following embodiments and the system using these devices. The technical idea of the present invention can be variously modified within the technical scope described in the claims.

(First embodiment)
As shown in FIG. 1, the in-vehicle device 1 according to the first embodiment of the present invention processes a detection processing unit 2 that detects pressing of a key of the steering remote controller 6 and various calculations performed by the in-vehicle device 1. , A processing unit 3 that controls the in-vehicle device 1, a storage unit 4 that stores various data, programs, and the like, a display unit 51, and an input unit 52. The in-vehicle device 1 is installed in a vehicle (not shown) and includes a car navigation system, a car audio, a video device, and the like.

  The steering remote controller 6 is a remote controller that is provided on a steering wheel (not shown) of the vehicle and outputs a signal for operating the in-vehicle device 1 to the in-vehicle device 1. For example, as shown in FIG. 2, the steering remote controller 6 is a voltage-dividing remote controller using a ladder circuit including a plurality of resistors R1 to R5 and a plurality of keys (switches) SW1 to SW5. The steering remote controller 6 outputs a different output voltage Vdc to the detection processing unit 2 of the in-vehicle device 1 with respect to the input voltage from the power source Vdd of the in-vehicle device 1 for each pressed key.

  The detection processing unit 2 includes a voltage detection unit 22 that detects the output voltage Vdc output from the steering remote controller 6 and input to the input port IN, and a pull-up resistor unit connected in series between the power supply Vdd and the input port IN. 21.

The output voltage Vdc input to the input port IN of the voltage detection unit 22 is stable even when the plurality of keys SW1 to SW5 are all open by the pull-up resistor unit 21. The output voltage Vdc when the key of the steering remote controller 6 is turned off when none of the keys is pressed and the output voltage Vdc when the keys SW1 to SW5 are pressed are different from each other. Resistance R _P of the pull-up resistor 21, even if any of the keys of the plurality of keys SW1~SW5 is depressed, the voltage detection unit 22 is optimized to detect the proper output voltage Vdc.

  The voltage detection unit 22 reads the input port IN periodically or with input fluctuation as a trigger, and detects the input output voltage Vdc. The voltage detection unit 22 AD converts a voltage value that is an analog value into a conversion value that is a digital value. For example, as shown in FIG. 3, the output voltage Vdc when the keys SW1 to SW5 are pressed, and the output voltage Vdc when no key is pressed are turned off by the power supply detection unit 22 as a 10-bit conversion value. D1 to D5 and Doff are converted and output to the processing unit 3.

  The processing unit 3 inputs the conversion values D1 to D5 output from the voltage detection unit 22, identifies which key SW1 to SW5 is pressed, and can execute the in-vehicle device 1 assigned to the pressed key. Perform the function. The processing unit 3 includes a display processing unit 31 that controls the display unit 51 to display various types of information, and a registration processing unit 32 that stores key assignments in the storage unit 4 and registers key functions. The processing unit 3 can be configured by a microcomputer.

  As shown in FIG. 3, the converted values indicating the output voltage Vdc when the key is pressed and turned off are included in the predetermined conversion value ranges d1 to d5 and the range doff, respectively. For example, when the converted value of the output voltage Vdc when any key of the steering remote controller 6 is included in the range d3 including the converted value D3, the processing unit 3 inputs the converted value D3 and presses the key SW3. It is determined that Ranges d1 to d5 and range doff are, for example, conversion values D1 to D5 and conversion value Doff, which are large and small predetermined ranges, respectively, and when the conversion values when two keys are pressed are close, they are separated at the midpoint of the two conversion values. It ’s fine.

  The storage unit 4 can store a series of programs necessary for processing performed by the in-vehicle device 1 and can be used as a temporary storage area required for processing. The storage unit 4 includes, for example, a main storage device including a volatile storage device such as SRAM and DRAM, and a nonvolatile storage device such as a magnetic disk such as a hard disk (HD), a magnetic tape, an optical disk, and a magneto-optical disk. An auxiliary storage device. In addition, as the auxiliary storage device, a RAM disk, an IC card, a flash memory card, a USB flash memory, a flash disk (SSD), or the like can be used.

  The display unit 51 is configured by a display device or the like. The input unit 52 includes an input device such as various switches and a connector for inputting a signal output from an external device. Moreover, the display part 51 and the input part 52 are good also as the touchscreen 5 as a structure which applied the input device and the display apparatus. In the first embodiment, the display unit 51 and the input unit 52 will be described as the touch panel 5.

<Key assignment method>
A key assignment method for assigning a function for controlling the operation of the in-vehicle device 1 to a key of the steering remote controller 6 will be described with reference to the flowchart of FIG.

  First, in step S <b> 1, the voltage detection unit 22 detects the output voltage Vdc when the steering remote controller 6 is not pressed, and outputs the converted value of the detected output voltage Vdc to the processing unit 3. The registration processing unit 32 of the processing unit 3 causes the storage unit 4 to store a conversion value indicating the off-state output voltage Vdc detected by the voltage detection unit 22.

  In step S2, the processing unit 3 shifts from the normal mode to the registration mode by a user operation on the touch panel 5. Next, the processing unit 3 determines that any of the keys SW1 to SW5 of the steering remote controller 6 has been pressed due to a change in the conversion value indicating the output voltage Vdc detected by the voltage detection unit 22.

  When it is determined that any of the keys SW1 to SW5 is pressed, the registration processing unit 32 causes the storage unit 4 to store a conversion value indicating the output voltage Vdc when the key is pressed in step S3. For example, when any one of the keys SW1 to SW5 is continuously pressed for a predetermined time (for example, 1 to 2 seconds), the registration processing unit 32 stores a conversion value indicating the output voltage Vdc when the key is pressed. Remember me. As shown in FIG. 5, the display processing unit 31 highlights one small area on the touch panel 5, which is displayed on a part of the display screen of the touch panel 5 and displays a plurality of small areas. Let The number of the plurality of small areas constituting the key display area 81 is equal to or more than the plurality of keys provided in the steering remote controller 6. The registration processing unit 32 may store the conversion value indicating the output voltage Vdc at the time of pressing the key in the storage unit 4 when the key is pressed without pressing the key continuously for a predetermined time.

  In step S4, the registration processing unit 32 registers a function that can be executed by the in-vehicle device 1 with respect to the converted value indicating the output voltage Vdc of the key pressed in step S2 by an input from the user. For example, as illustrated in FIG. 5, the display processing unit 31 displays a list of functions that can be executed in the in-vehicle device 1 in a function display area 82 that is a part of the display screen of the touch panel 5. When the user selects and performs an input operation on any of the function display areas 82 in which each function is displayed, and the touch panel 5 designates the function to the processing unit 3, the registration processing unit 32 performs step S2. A function to be assigned to the pressed key is registered and stored in the storage unit 4. The display processing unit 31 displays the registered function name in one small area of the key display area 81 highlighted in the immediately preceding step S3. Therefore, the user can list the functions already registered in the keys of the steering remote controller 6. The function display area 82 can display a list by scrolling or the like when the number of function items to be displayed is large.

  In step S5, the processing unit 3 determines whether or not the function registration for the keys of the steering remote controller 6 has been completed. If it is determined that the registration is not yet completed, the processing unit 3 returns to step S2, and if it is determined that the registration is completed, the processing unit 3 ends the registration mode and shifts to the normal mode. The determination in step S5 may be performed by a user operation on the touch panel 5.

  In the normal mode, the processing unit 3 receives the conversion value determined as the conversion value indicating the voltage stored in the storage unit 3 in step S3 from the voltage detection unit 22, and the storage unit 3 in step S3 The function registered in step S4 is executed on the converted value indicating the stored voltage.

  According to the vehicle-mounted device according to the first embodiment, by storing the output voltage for each key of the steering remote controller and identifying the key, it can be easily performed by various steering remote controllers regardless of the vehicle manufacturer and the vehicle type. Operation is possible.

  Moreover, according to the vehicle-mounted apparatus which concerns on 1st Embodiment, even if it is a steering remote control from which a shape and key arrangement differ, a function can be freely allocated for every key.

  Further, according to the in-vehicle apparatus according to the first embodiment, in the registration mode, the conversion value indicating the output voltage at the time of pressing the key is stored in response to the key of the steering remote controller being pressed continuously for a predetermined time. By storing in the unit, noise such as chattering can be prevented, and the detection accuracy of the output voltage can be improved.

  The processing unit 3, the storage unit 4, and the like shown in FIG. 1 are displays as logical structures, and may actually be configured by arithmetic processing devices that are the same hardware, or may be configured by separate hardware. It doesn't matter.

(Second Embodiment)
The in-vehicle device 1a according to the second embodiment of the present invention has a structure in which the detection processing unit 2 in FIG. 1 is replaced with a detection processing unit 2a shown in FIG. As shown in FIG. 6, the resistance value of the pull-up resistor 21a of the detection processing unit 2a is variable and can be changed to an appropriate resistance value in the detection of the output voltage of the steering remote controller by the steering remote controller. It differs from the vehicle-mounted apparatus 1 which concerns on embodiment. Other configurations that are not described in the second embodiment are substantially the same as those in the first embodiment, and thus redundant description is omitted.

  7A to 7C, the steering remote controller 6A, 6B, 6E, and the table of FIG. 8, the steering remote controller has a structure such as the number of keys, resistance value, wiring, output voltage, etc. depending on the vehicle manufacturer and vehicle type. Is different.

Detection processing section 2a of the vehicle-mounted device 1a is provided, as shown in FIG. 6, the voltage detection unit 22, another pull-up resistor portion 21a, the pull-up resistor portion 21a, changing the resistance value R _P of the pull-up resistor portion 21a A resistor control circuit 24 that outputs a control signal CS to be output, and a control unit that inputs a conversion value indicating the output voltage Vdc detected by the voltage detection unit 22 from the voltage detection unit 22 and controls the operation of the resistor control circuit 24 23. The control unit 23 can be configured by a microcomputer.

For example, as shown in FIG. 9, the pull-up resistor unit 21a includes two pull-up resistors R ₁ connected in parallel between the input port IN for detecting the output voltage Vdc of the steering remote controller 6 and the power supply voltage Vdd. provided with R _2, and switching elements Tr1, Tr2 for controlling conduction of the pull-up resistor _{R 2.}

Switching elements Tr1 of the pull-up resistor portion 21a is turned on by the control signal CS output from the resistor control circuit 24 is controlled off, by controlling the conduction of the pull-up resistor R _2, the pull-up resistor portion 21a You can change the resistance value _{R P.}

The number of pull-up resistors and the number of switching elements provided in the pull-up resistor unit 21a are not limited to 1 and 2, but may be 3 or more. In this case, a control signal output from the resistor control circuit 24 the CS, can change the resistance value _{R P} of the pull-up resistor portion 21a 3 or more. Further, the pull-up resistor portion 21a may be a variable resistor stepless, similarly, the control signal CS output from the resistor control circuit 24 can arbitrarily change the resistance value R _P.

Control unit 23 in advance predetermined and plurality of resistance R _P, the control signal CS for changing the resistance value R _P of the pull-up resistor portion 21a in a predetermined plurality of resistance R _P, output resistor control circuit 24 The settings to be retained are retained.
The output terminals Q ₁ and Q ₂ of the steering remote controller 6 are directly connected to the input terminals P ₁ and P _{2 of the} in-vehicle device 1a, respectively.

<Method of determining the resistance value _{R P>}
With reference to the flowchart of FIG. 10, a method of determining the resistance value R _P of the pull-up resistor portion 21a in the registration mode.

First, when no key of the steering remote controller 6 is pressed, the control unit 23 causes the resistor control circuit 24 to store a resistance value R _P of the pull-up resistor unit 21a and a plurality of predetermined resistance values R _P. The control signal CS to be sequentially changed is output. Registration processing unit 32 of the processing unit 3, shown in accordance with the resistance value R _P of the pull-up resistor portion 21a is sequentially changed, at the OFF time of the steering remote control 6, the output voltage Vdc for each resistance value R _P The converted value is stored in the storage unit 4.

  In step S11, the voltage detection unit 22 detects the output voltage Vdc when any key of the steering remote controller 6 is continuously pressed for a predetermined time, and outputs the converted value of the detected voltage Vdc to the control microcomputer 23. . Assume that the control unit 23 presses any one of the keys SW1 to SW5 of the steering remote controller 6 due to a change in the conversion value indicating the output voltage Vdc detected by the voltage detection unit 22.

In step S12, the control unit 23, the resistor control circuit 24, the resistance value R _P of the pull-up resistor portion 21a, to output a control signal CS to sequentially change a plurality of predetermined resistance value R _P of holding. Depending on the resistance value R _P of the pull-up resistor portion 21a is sequentially changed, the registration processing unit 32, conversion value showing the pressed key steering remote controller 6, the output voltage Vdc for each resistance value R _P Is stored in the storage unit 4.

For example, the control unit 23 are two of the resistance value _{R P1, R P2,} and the resistance value of the pull-up resistor portion 21a a control signal CS to change the two resistance values _{R P1, R P2} the resistor control circuit 24 When holding the setting to be output, when the key SW1 of the steering remote controller 6 is pressed in step S11, the steering remote controller 6 outputs two types of output voltages Vdc for the key SW1 in step S12.

  In step S <b> 13, the processing unit 3 determines whether or not the processing in steps S <b> 11 to S <b> 12 has been completed for all keys of the steering remote controller 6. If the processing unit 3 determines that the process is not completed for all keys, the process returns to step S11. If the process unit 3 determines that the process is completed for all keys, the process proceeds to step S14. The determination in step S13 may be performed by a user operation on the touch panel 5.

In step S14, the processing unit 3, a predetermined plurality of control unit 23 holds the resistance value per R _P, the conversion value indicative of the output voltage Vdc at the output voltage Vdc and off for each of the plurality of keys of the steering remote controller 6 create an output voltage list is information based on the output voltage list, select the optimum resistance value R _P to identify the pressed key, it terminates.

For example, processing unit 3 refers to the output voltage list created for each of the resistance value R _P, adjacent the plurality of output voltage Vdc consisting output voltage Vdc and the output voltage Vdc upon pressing a plurality of keys in the OFF the difference between the voltage value becomes largest resistance value R _P to be selected as an optimum resistance value R _P. The resistance value R _P of the difference becomes the largest of the minimum and maximum voltage values of the plurality of output voltages Vdc, may be selected as an optimum resistance value R _P. The processing unit 3, of the output voltage Vdc and the output voltage Vdc upon pressing a plurality of keys during off, by excluding the resistance value R _P of the difference between the adjacent voltage value is equal to or less than a predetermined value, the resistance The value _RP may be selected.

In the normal mode, the control unit 23, in a state where the control was such that the resistance value R _P selected by the processing section 3 to the pull-up resistor portion 21a, the voltage detector 22 detects an output voltage Vdc of the steering remote control 6 Then, the processing unit 3 identifies the key of the pressed steering remote controller 6.

  According to the vehicle-mounted device according to the second embodiment, by storing the output voltage for each key of the steering remote controller and identifying the key, it is possible to easily use various steering remote controllers regardless of the vehicle manufacturer and the vehicle type. Operation is possible. Further, in order to detect the voltage value input from the steering remote controller, a dedicated circuit is provided for each vehicle manufacturer or vehicle type, and it is not necessary to switch the circuit to detect the voltage value.

Further, the vehicle-mounted device 1a of the second embodiment, since the resistance value R _P of the pull-up resistor portion 21a is variable, the voltage detection unit 22 can accurately detect voltage Vdc. Therefore, erroneous identification of keys can be reduced.

  Moreover, according to the vehicle-mounted device according to the second embodiment, it is not necessary to prepare a dedicated cable for each vehicle, to prepare a means for relaying communication separately, and for the user to switch the setting. It can be easily operated by various steering remote controllers.

  Moreover, according to the vehicle-mounted apparatus which concerns on 2nd Embodiment, even if it is a steering remote control from which a shape and key arrangement differ, a function can be freely allocated for every key.

(Other embodiments)
Although the present invention has been described with reference to the above-described embodiments, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

In the second embodiment already described, in order to increase the identification accuracy of the key, the processing unit 3 has a plurality of resistance values held by the control microcomputer 23 when the key of the steering remote controller 6 is pressed even in the normal mode. sequentially switched to R _P, it may be performed to identify the key by using the respective output voltage Vdc.

  In addition to the above, of course, the present invention includes various embodiments and the like not described here, such as configurations to which the first and second embodiments are applied. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

DESCRIPTION OF SYMBOLS 1, 1a ... In-vehicle apparatus 2, 2a ... Detection processing part 3 ... Processing part 4 ... Memory | storage part 5 ... Touch panel 6 ... Steering remote control 21, 21a ... Pull-up resistance part 22 ... Voltage detection part 23 ... Control microcomputer 24 ... Resistor control Circuit 51 ... Display section 52 ... Input section 81 ... Key display area 82 ... Function display area

Claims (7)

A voltage detection unit that includes an input port connected to a voltage dividing type remote controller that outputs a different output voltage for each key pressed by the user, and that detects an output voltage output from the remote controller from the input port;
A pull-up resistor unit connected in series between a power source that outputs a voltage to the remote controller and the input port, and having a variable resistance value;
A control unit that controls the pull-up resistor unit to sequentially change to a plurality of resistance values while the key is pressed;
An in-vehicle device, comprising: a processing unit that selects a resistance value of the pull-up resistor unit based on an output voltage for each of the plurality of resistance values while the key is pressed.   For the plurality of resistance values, the pulling unit that maximizes the difference between adjacent output voltage values of the output voltage when the key is not pressed and the output voltage of the keys for each of the plurality of resistance values. The in-vehicle device according to claim 1, wherein a resistance value of the up resistor portion is selected.   For the plurality of resistance values, the processing unit has the largest difference between the minimum and maximum voltage values of the output voltage when the key is not pressed and the output voltage for each key. The in-vehicle device according to claim 1, wherein a resistance value of the pull-up resistor unit is selected.   The control unit controls the pull-up resistor unit to sequentially change to a plurality of resistance values in response to the key being continuously pressed for a predetermined time. The in-vehicle device according to any one of the above. Detecting an output voltage output from the remote controller from an input port connected to a voltage dividing remote controller that outputs a different voltage for each key pressed by the user;
While the key is pressed, the pull-up resistor unit that is connected in series between the power source that outputs a voltage to the remote controller and the input port and has a variable resistance value is sequentially changed to a plurality of resistance values. Step to control, and
Selecting a resistance value of the pull-up resistor unit based on an output voltage from the remote controller for each of the plurality of resistance values while the key is pressed;
And a step of identifying a pressed key based on an output voltage output from the remote controller in a state where a resistance value of the pull-up resistor unit is selected.   In the selecting step, for the plurality of resistance values, the difference between adjacent output voltage values in the plurality of output voltages including the output voltage when the key is not pressed and the output voltage for each key is maximized. 6. The key identification method according to claim 5, wherein a resistance value of the pull-up resistor unit is selected.   In the selecting step, for the plurality of resistance values, the difference between the minimum and maximum voltage values in the plurality of output voltages composed of the output voltage when the key is not pressed and the output voltage for each key is the largest. The key identification method according to claim 5, wherein a resistance value of the pull-up resistor unit is selected.

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